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Blue Sea add a battery wiring

Old 11-21-2017, 12:47 PM
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Default Blue Sea add a battery wiring

I have an 18' center console that is currently set up with 2 12v batteries running parallel. It's time to get new batteries and I want to switch to an isolated start and house battery. I am going to run the Blue Sea add a battery system. I have seen quite a few different variations of wiring that people have previously posted on this forum. I am planning on sticking to the diagram from what is shown with the product. However, I have a few questions regarding wiring. I have a Yamaha 115 4-stroke outboard and want to know what would be the proper gauge wire for running the positive wires from the master switch to switch panel, house and start battery, etc. Also, what amp rating resettable circuit breaker do you suggest running from both the positive terminals of the house and start battery to the ACR charger?
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Old 11-21-2017, 05:35 PM
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For determining the proper gauge of wire requires you to define the length of run, amps and run time. Go to the Blue seas website and use the Blue Sea’s Circuit Wizard to determine the appropriate gauge cable.
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Old 11-21-2017, 09:54 PM
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Your fuse size from the positive battery terminals to Terminals A and B will be determined by your charging amps. So that's the larger of the output of your outboard (which I believe is about 25A for an F115) or your battery charger (if it's hooked up through your ACR).

Blue Sea gives the following guidance:

up to 60 charging amps => 75 to 90 amp fuse or breaker
80 amps => 100-125 amp fuse or breaker
100 amps => 150 amp fuse or breaker
120 amps => 175 amp fuse or breaker
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Old 11-21-2017, 10:21 PM
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Thanks for that information... sounds like I will go with 2x of these @ 80 amp rating

https://powerwerx.com/resettable-cir...IaAgwlEALw_wcB
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Old 11-21-2017, 11:50 PM
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the charging amps actually has nothing to do with it, despite blue sea saying it is. if one battery is low, and a 30a alternator starts charging the full one, when the ACR combines the good with the low one you could have hundreds of amps flowing from one to the other. I have seen 200a MRBF fuses blow on an ACR with a 40a charger causing it. but that was a huge low house bank. not going to happen with a group 24 feeding a 24.

I would run 2awg from both batteries to the switch. and to the ACR. with dual MRBF fuse holders on each battery. one each for the acr and one for the switch feed. like 150a on the acr feeds and 200a on the switch feeds. that should be ok to crank the motor. keep spares. if the motor one ever blows. move to a 300a on the start battery and leave the 200 on the house one.

the one to the house panel really depends on what you are running on it, and the length. and could vary a lot. if the batteries and swtich are in the console. you'd proably be ok with 8 or 6awg. but depends how much electrical you have on the boat.
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Old 11-24-2017, 09:26 AM
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Originally Posted by smac999 View Post
the charging amps actually has nothing to do with it, despite blue sea saying it is. if one battery is low, and a 30a alternator starts charging the full one, when the ACR combines the good with the low one you could have hundreds of amps flowing from one to the other. I have seen 200a MRBF fuses blow on an ACR with a 40a charger causing it. but that was a huge low house bank. not going to happen with a group 24 feeding a 24.
That's interesting. I never thought of that scenario. Just for my own understanding (sorry to hijack the thread) - is this a case of having a full starter battery (say 12.6V or more) all of a sudden combined with a really low house bank (say at 10V) through the ACR, causing a high amperage/short burst of current that would quickly equalize the battery potentials (at which point the ACR would open...or alternate opened/closed as it's supposed to to bring both batteries up)? Makes sense in that case that the charging amps in that scenario have nothing to do with the max current you could expect to see in the connection between the batter positives to ACR terminals.
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Old 11-25-2017, 07:16 AM
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Originally Posted by HulaGirlNC View Post
Thanks for that information... sounds like I will go with 2x of these @ 80 amp rating

https://powerwerx.com/resettable-cir...IaAgwlEALw_wcB
Those fuses are there to protect the wire. Make sure you size your wire so an 80 amp breaker will protect it. Assuming the run is not very long that would be around a 6 gauge wire.
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Old 11-25-2017, 07:03 PM
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Here's how I would wire it. If you look closely at both ways it is practically the same EXCEPT the ACR turns off when you turn the switch off (no parasitic drain)... another advantage is you use much less wire. Each lead could be as short as 6" so there would really be no need to fuse the wires.

Cut me some slack on my Samsung edit job. Can someone give one disadamage to wiring it this way? I see none.

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Last edited by mdees88; 11-25-2017 at 07:51 PM.
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Old 11-26-2017, 12:09 PM
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Originally Posted by mdees88 View Post
Here's how I would wire it. If you look closely at both ways it is practically the same EXCEPT the ACR turns off when you turn the switch off (no parasitic drain)... another advantage is you use much less wire. Each lead could be as short as 6" so there would really be no need to fuse the wires.

Cut me some slack on my Samsung edit job. Can someone give one disadamage to wiring it this way? I see none.

Attachment 1021098
With your design you are now using the battery cables as part of the circuit.
The circuit length would be from the battery to the ACR no matter what route and will require a fuse if running through conduit from the helm to the batteries. Now if the switch is right beside the batteries and ACR it will work.
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Old 11-26-2017, 01:56 PM
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Originally Posted by davepjr71 View Post
With your design you are now using the battery cables as part of the circuit.
The circuit length would be from the battery to the ACR no matter what route and will require a fuse if running through conduit from the helm to the batteries. Now if the switch is right beside the batteries and ACR it will work.
Yes, my crank and house battery are right next to the switch and ACR. I agree it would need to be fused if you have a long run of wire from your battery to your switch... every boat I have owned has had the batteries and switch located in the same place
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Old 11-26-2017, 02:40 PM
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Originally Posted by mdees88 View Post
Here's how I would wire it. If you look closely at both ways it is practically the same EXCEPT the ACR turns off when you turn the switch off (no parasitic drain)... another advantage is you use much less wire. Each lead could be as short as 6" so there would really be no need to fuse the wires.

Cut me some slack on my Samsung edit job. Can someone give one disadamage to wiring it this way? I see none.

Attachment 1021098
I often do this, but still on the battery side of swtich.
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Old 11-26-2017, 03:07 PM
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Originally Posted by smac999 View Post
I often do this, but still on the battery side of swtich.
That will save you some wire verses the original way. Only problem is if you wire it on the battery side of the switch the ACR never turns off and still has a parasitic drain on the batteries.

By wiring it to the load side of the switch the ACR turns off when you turn the battery switch off.


All 3 ways should work fine. I just like it this way do when you turn your switch off EVERYTHING in the boat is off...
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Old 11-26-2017, 04:16 PM
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the battery side is just a good habit. as having an ACR on the load side can cause many bad things. not in this case with the single switch. but in more advanced systems. or if you replace that switch with two on / off switches. it'll cause havoc.

draw doesn't matter to me. every client boat is plugged in 24/7.
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Old 11-27-2017, 03:47 AM
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Originally Posted by smac999 View Post
the battery side is just a good habit. as having an ACR on the load side can cause many bad things. not in this case with the single switch. but in more advanced systems. or if you replace that switch with two on / off switches. it'll cause havoc.

draw doesn't matter to me. every client boat is plugged in 24/7.
Agreed, and the user can always pull the Negative fuse for the ACR if they don't want it monitoring all the time. I do that every winter.
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Old 12-14-2017, 12:01 PM
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Originally Posted by mdees88 View Post
Yes, my crank and house battery are right next to the switch and ACR. I agree it would need to be fused if you have a long run of wire from your battery to your switch... every boat I have owned has had the batteries and switch located in the same place
So are you saying that it is not necessary for me to fuse the line from the ACR to the + terminal of both house and start battery?
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Old 12-14-2017, 12:34 PM
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Originally Posted by HulaGirlNC View Post
So are you saying that it is not necessary for me to fuse the line from the ACR to the + terminal of both house and start battery?
All that fuse is protecting is the length of wire from the ACR to the battery post....

ABYC standard for fuses is they should be placed within 7" of the source of power (battery in this case). Say the total length of wire from the ACR to battery is 2ft. Let's say you put a fuse at 7". This means 7" of wire is unprotected and 17" is protected. For that fuse to trip something would have to happen in the 17" of wire to cause a short.

If you wire the way I showed you use less than 1ft of wire rendering the fuse pointless...

IMO you do not need to fuse those wires.... especially if you keep your wires as short as possible and have them ran where "random stuff" (tools, tackle box) will not touch the wires.
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Old 12-14-2017, 12:37 PM
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Originally Posted by HulaGirlNC View Post
So are you saying that it is not necessary for me to fuse the line from the ACR to the + terminal of both house and start battery?
If the ACR is close to the batteries it's not necessary. Blue seas used to state they were optional but have since changed to include them. Probably due to people giving them grief about something they know say they should be in.
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Old 12-14-2017, 02:24 PM
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Thanks for clearing that up. The ACR will be in close proximity so I will go with no fuses.
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